durham ranch seismic acquisition

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Durham Ranch Seismic Acquisition

Colorado USA, Using ION FireFly

Organization - Chronological

0. Overview1. Scouting / Permitting2. Designing / Surveying3. Shothole Drilling4. Seismometer Deployment5. Shooting / Recording6. Processing

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Durham RanchMoffat County, Northwestern Colorado

Sand Wash Basin

CO

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Durham RanchA Closer View

• 31 square miles. Elevation ranges from 7500 to 9000 feet above sea level

• Breached anticline: Sandstone over shale.

• Significantly varying topography, ranging from irrigated farmland to exposed cliffs to high mountain meadows.

• Livestock and wildlife are prevalent. Prime hunting location in Colorado.

• The BLM has numerous restrictions in place to protect native species, including birds-of-prey, deer, and black bear.Satellite image courtesy of Google Earth

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Durham Ranch - Producing Wells

• The Durham Ranch area contains a number of oil wells that average between 50-100 barrels per day.

• However, multiple dry holes have also been drilled since the field was discovered in the 1950’s. No 3D seismic had ever been shot here.

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Durham Ranch: The Reservoir TargetFractured Carbonates in the Niobrara Formation

• An outcrop of the target Niobrara reservoir alongside the Green Mountain Reservoir, just north of Silverthorne, CO.

• Left: thin laminations of a section of the carbonate reservoir that is not highly fractured.

• Middle/right: fracturing becomes more intense.

• Expected Niobrara levels from ~ 1200ft-3000ft in project area

Organization - Chronological

0. Overview

1. Scouting / Permitting

2. Designing / Surveying

3. Shothole Drilling

4. Seismometer Deployment

5. Shooting / Recording

6. Processing

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Acquisition TimelineFireFly Survey at Durham Ranch

FEB MAR APR MAY JUN JUL AUG SEP

Permitting

Shot-hole drilling

Crew mobilization

System deployment

Shooting

System retrieval

Processing

• Significant time constraints. – Hunting season starts

September 1. – All seismic acquisition

operations must be completed by this date.

• East Resources invited several seismic contractors to bid on the project, with many submitting ‘no-bids’

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Planning: Winter Scouting

Organization - Chronological

0. Overview1. Scouting / Permitting2. Designing / Surveying3. Shothole Drilling4. Seismometer Deployment5. Shooting / Recording6. Processing

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LIDAR Basics

Reflection Pointsfrom surface featuresfrom ground features

•Lidar collects elevation points of surface features (full feature model).

•Lidar can also image the surface beneath the canopy (bare earth model). As long as light can penetrate the canopy, the laser will also penetrate the canopy and you will get hits off the ground surface underneath.

•Lidar is independent of sun angle and can be collected day or night.

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LiDAR – “Bare Earth”

Sagebrush & Vegetation

Steep Gully

Drill Site

(1mi x 1mi - Wyoming)

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LiDAR – “Full Feature”

Sagebrush & Vegetation

Drill Site

Steep Gully

(1mi x 1mi - Wyoming)

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LiDAR – “Slope Analysis”

LEGEND: % slope

grey 0-5%R 5-10%O 10-15%Y 15-20%G 20-25%B 25-30%I 30-35%V >35%

(1mi x 1mi - Wyoming)

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LIDAR Canopy = Full Feature – Bare Earth

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LiDAR 3D Visualization ‘Fly Through’

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21st Century Imaging Challenges

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Seismic Data: Wavelength > 30m

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Traditional geometry

600 m

station interval: 25 m

line interval: 400 m

recording template:8 lines x 100 stations

Challenge: Shot/Receiver Density

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Challenge: Shot/Receiver Density

station interval: 25 m

line interval: 125 m

recording template:20 lines x 100 stations

Densely sampled geometry

600 m

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Challenge: Shot/Receiver Density

station interval: 25 m

line interval: 25 m

recording template:100 lines x 100 stations

Fully sampled geometry

600 m

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Survey ParametersDensely Sampled, Full-wave Multi-client Survey

BLM controlled area is shown in yellow.

• Geophones: 6,100

• Receivers: 10,597 (327 “miles”)

• Sources: 7,271 (223 “miles”)

• Traces: about 10 million

• Receiver Density: 346/ square mile

• Nominal fold: 240

• Area: 31 square miles

• Surface relief: 2000 feet

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Staking – Lets not!

Survey Supplies –Daily

Induced Receiver Location Error Induced Source Location Error

Organization - Chronological

0. Overview

1. Scouting / Permitting

2. Designing / Surveying

3. Shothole Drilling

4. Seismometer Deployment

5. Shooting / Recording

6. Processing

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Shotpoint Planting: Stakeless Drilling

• Dynamite Sources

• No surveying & staking

• Faster, Cheaper

• Less HSE risk

• More Accurate

Organization - Chronological

0. Overview1. Scouting / Permitting2. Designing / Surveying3. Shothole Drilling4. Seismometer Deployment5. Shooting / Recording6. Processing

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Wireless Field Station Unit

Full-wave, multi-component MEMS

digital sensors

FireFly recording unit with Bluetooth, VHF, processor

and flash memory

No wires for communication and power, anyway….

FSU Deployment - Navtool

Crew 3 Coordinates and elevation of actual receiver position are entered into trace headers

Also:

Digital Compass

Orientation Pole

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Easy Operational Environment

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Not as easy as it seems…

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Not as easy as it seems

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Not as easy as it seems

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FSU Deployment: VSI training and crew

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FSU Deployment : Mini-me

• Miniaturized NavTool deployment pole for climbing crews– Allows climbers to carry pole

on their backs

FSU Deployment: Horizontal Deployment

Bonded with drywall paste

Weighted by Sandbag

Vertical Buried Sensor not shown in picture

All three sensors have nearly identical response

Good that Vectorseis is insensitive to angle…

FSU Deployment

Field crews deploy gear where it is safe. Trace headers will contain actual coordinates and elevations where the gear is deployed.

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DeploymentGPS and LiDAR DEM for positioning

Shooting

System: Ethernet, VHF, Bluetooth, GPS

Doghouse

AccurateSEGY headers

in real time

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FSU Deployment: River Crossing

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Communication: Heliportable Towers

Organization - Chronological

0. Overview• Scouting / Permitting• Designing / Surveying• Shothole Drilling• FSU Deployment• Shooting / Recording• Processing

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Conventional Source Control• Voice communications make it difficult to manage large number of

shooting crews

“Hey Shooter2, sorry to keep asking, but are you guys finally ready yet?

You’ve been working on that hole for the past 10

minutes.”

“We’re almost ready –the leads were buried

in the ice. Give us about 10 more minutes

and maybe we’ll be ready to go.”

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Automated Source Control

• Shooting efficiency increased by eliminating non-emergency voice communications

• Simplifies management of large shooting crews

“Shooter2 Ready?”

“Yes”

“No.”

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Shooting

• Average 318 shots / day

• Maximum 723 shots / day

• Shooting completed in 20 days

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Shots Recorded by Day

Daily Average = 318

Battery Swap Day

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August 25: 723 Shots

This was Firefly v2.0, 2.1 now in production

• FireFly v2.1:– Power reduced by 20%-35%– RF bandwidth increased by 150%-230%– Trace attributes– Analog sensor via Geophone Digitizing Unit– RTK GPS– Continuing massive software development

• V2.2 currently in testing…

Organization - Chronological

0. Overview

1. Scouting / Permitting

2. Designing / Surveying

3. Shothole Drilling

4. FSU Deployment

5. Shooting / Recording

6. Processing

Processing: Anisotropy and Converted Wave

• HTI and migrations - Scott Schapper and Rob Jefferson

• VTI, HTI and migrations - Ed Jenner

• Converted wave – Mike Stewart and Alex Calvert

OVT PSTM, TLE Publication

“Anisotropic Velocities and Offset Vector Tile Pre-stack Migration Processing of the Durham Ranch 3D, Northwest Colorado”

The Leading Edge; November 2009; v. 28; no. 11

Scott Schapper1, Robert Jefferson1, Alexander Calvert1, and Marty Williams2

1Ion Geophysical, GXT Imaging Solutions, Denver, CO, USA

2East Resources, Broomfield, CO, USA

( Waddle Creek oil field = subset of Durham Ranch )

NW SE NW SEWaddle Creek FieldWaddle Creek Field

The isotropic migration on the left does not fully image the buried focus at 1.5 sec. The VTI anisotropic migration (η=0.1) on the right properly images the buried focus, revealing what appears to be sediments folded atop faulted basement.

OVT PSTM: Isotropic versus VTI

Basement Basement

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Processing Flow: Migration ↔ AZIM

Geometry (pre-processing) and Refraction Statics

First pass Velocities and Residual Statics

Signal Processing

Second Pass Velocities and Residual Statics

AZIM™, 3rd Pass Res. StaticsTest PSTM

Trim Statics

FXY Decon

Stack & Post-Stack TM

Post-Migration Enhancements

OVT Pre-Stack TM eta=0.1

AZIM™ Analysis and Correction

Post-Migration Enhancements

• 9,220,050 traces• 8776 receivers• 6683 sources

[ 52 ]Fold – all offsets (color scale set to 1 – 168)

CMP fold map – full fold

OVT: Sectoring by Azimuth and Offset

NW NWSE SEWaddle Creek FieldWaddle Creek Field

Anisotropic PSTM: Common Offset versus OVT

Both migrations account for VTI anisotropy with η= 0.1. The two images are comparable in the deep section, but the OVT image appears to suffer more from shallow sampling deficiencies.

Niobrara

Entrada

Basement

Niobrara

Entrada

Basement

Vf-V

s (ft

/s)

0

2500

Anisotropy analysis after OVT PSTM

The OVT migrated attribute appears to be better positioned relative to interpreted faulting (magenta arrow), and fault influence on this attribute is also more apparent. The deeper high Vfast-Vslow anomaly (yellow arrow) has decreased in magnitude and moved closer to the lateral ramp deformation zone, suggesting that the dip effect has been removed, but the possible influence of lateral velocity variation may remain.

Basement Basement

EntradaEntrada

Niobrara Niobrara

7500 ft7500 ft

7500 ft7500 ft

Azimuthal attributes at Entrada Horizon

Unmigrated OVT PSTM

Interval Vfast -V

slowAnisotropy direction and coherency

VTI, HTI and migration; TLE article

“Combining VTI and HTI anisotropy in prestack time migration: Workflow and data examples”

The Leading Edge; July 2011; v. 30; no. 7

Edward Jenner1

1Ion Geophysical, GXT Imaging Solutions, Denver, CO, USA

Workflow

Input gathers for PSTM

Possibly Common-Offset PSTM

VTI parameter estimation

VTI OVT PSTM

HTI velocity analysis (AZIM)

Residual VTI analysis

HTI velocity analysis (AZIM)

VTI+HTI OVT PSTM

Residual HTI velocity analysis

Current VTI Workflow VTI+HTI Workflow

Combined VTI and HTI migration

Portion of OVT prestack time migrations migrated with a) VTI velocity field, b) VTI velocity field with residual VTI and HTI corrections and c) combined VTI+HTI velocity field followed by residual HTI correction.

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Converted Waves

S R

P to S conversion point Mid point

Vp:Vs

6

4.5

3

2.5

2

Asymptotic conversion zone

Conversion point closer to receiver whenhigher Vp:Vs ratio

PW SW

C-Wave Scoping Workflow

• Receiver Gather Analysis/Comparison (Z, H1, H2, Radial, Transverse)– Radial/Transverse QC– check for p-wave leakage or mode conversions, or valid c-wave energy

• Signal processing (noise attenuation, decon, bandpass)

• Receiver gather velocity analysis (determine if Vc is too similar to Vp)

• Receiver stacks (initial look at structure, receiver statics)

• Sectored receiver stacks (investigate structure, splitting)

C-Wave scoping

What we would like to see for radial and transverse...

... if splitting were present.

(Not from Durham Ranch)

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0 90 180 270 360

FAST direction (peaks)

SLOW direction (troughs)

Radial: azimuth sectored gathers

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0 90 180 270 360 Polarity reversal.These correspond to

FAST & SLOWazimuth directions

Transverse: azimuth sectored gathers

Raw Radial Receiver Gather ( Azimuth Sect. )

• Not sinusoidal, but azimuthally varying due to structure

0 90 180 270 360

Raw Transverse Receiver Gather ( Azimuth Sect. )

• No Polarity Flips, but azimuthally varying due to structure

C-Wave Scoping: Conclusions

• C-Wave signal is most likely upcoming P converting on shallow interface or free surface effect

• Ground roll disturbs C-Wave signal at interesting offsets & depths

• Can not determine a useful Vc due to p-wave leakage

• Azimuth sorted Radial and Transverse receiver gathers show significant azimuthal effects due to structure and possibly anisotropy. But derivation of fracture direction is not possible.

• Radial component azimuth sectored common receiver stacks using the derived 1D velocity function from the supergather, shows poor stack quality and holes. Could make derivation of receiver statics challenging.

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1500

1000

500

T

ime

(ms)

a b c

a) raw gathers with spherical divergence correction

b) with noise attenuation c) with deconvolution

Representative shot gather signal processing progression

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Processing Comments

• The PSTM volumes improve imaging around deeper fault-areas in a manner that appears to be geologically-reasonable.

• The inclusion of Eta within the PSTM appears to produce further improvements around these deeper faults.

• AZIM™ attributes determined post OVT-PSTM appear to be more consistent with structure and faulting. These volume appear to be improved relative to AZIM™ volumes produced from unmigrated data.